how to get data from other page?

Question

I have page a and page b.
In page a, open page b.
in page b, user input some data, after close page b,
How to let a get the data in b.
I code below, but not get.
in page a:
LiveStreamPage liveStreamPage = new LiveStreamPage();
await Navigation.PushAsync(liveStreamPage);
if (liveStreamPage.url != "")
{
((MainViewModel)DetailPage.BindingContext).OnAppearing(liveStreamPage.url);
}
this.IsPresented = false;
in page b, the b is LiveStreamPage
public partial class LiveStreamPage : ContentPage
{
public String url = "";
public LiveStreamPage()
{
InitializeComponent();
}

    private async void Button_Clicked(object sender, EventArgs e)
    {
        url = editor.Text.Trim();
        await Navigation.PopAsync();
    }
}

Answer 1

Hi 80240195,

Welcome to our Microsoft Q&A platform!

If you want to transfer the data from page b to page a, usually we use delegate to refresh the "parent page".

Here is a simple demo using delegate to transfer data between pages.

MainPage.xaml

<Label x:Name="result"/>  
<Button Text="SubPage" Clicked="Button_Clicked"/>  

MainPage.xaml.cs

public partial class MainPage : ContentPage  
{  
    // ...  
    private async void Button_Clicked(object sender, EventArgs e)  
    {  
        SubPage subpage = new SubPage();  
        //register event  
        subpage.TransfEvent += frm_TransfEvent;  
        await Navigation.PushAsync(subpage);  
    }  
  
    void frm_TransfEvent(string value)  
    {  
        result.Text = value;  
    }  
}  

SubPage.xaml

<Entry TextChanged="Entry_TextChanged"/>  

SubPage.xaml.cs

public partial class SubPage : ContentPage  
{  
    // ...  
    public event TransfDelegate TransfEvent;  
  
    private void Entry_TextChanged(object sender, TextChangedEventArgs e)  
    {  
        TransfEvent((sender as Entry).Text);  
    }  
}  
  
public delegate void TransfDelegate(String value);  

---

Besides, we prefer to use MVVM pattern in Xamarin.Forms project. We can use data binding to transfer data.

The following is an MVVM example.

MainPage.xaml

<Label x:Name="result" Text="{Binding Result}"/>  
<Button Text="SubPage" Command="{Binding ToSubPageCommand}"/>  

MainPage.xaml.cs

public partial class MainPage : ContentPage  
{  
    public MainPage()  
    {  
        InitializeComponent();  
        this.BindingContext = new MainPageViewModel(this.Navigation);  
    }  
}  

SubPage.xaml

<Entry Text="{Binding Result}"/>  

MainPageViewModel.cs

class MainPageViewModel : INotifyPropertyChanged  
{  
    public ICommand ToSubPageCommand { get; private set; }  
    public INavigation Nav;  
    string result;  
    public string Result  
    {  
        get => result;  
        set  
        {  
            result = value;  
            OnPropertyChanged("Result");  
        }  
    }  
  
    public MainPageViewModel(INavigation nav)  
    {  
        ToSubPageCommand = new Command(ToSubPage);  
        Nav = nav;  
    }  
  
    SubPage subpage = new SubPage();  
  
    async void ToSubPage()  
    {  
        subpage.BindingContext = this;  
        await Nav.PushAsync(subpage);  
    }  
  
    public event PropertyChangedEventHandler PropertyChanged;  
  
    protected void OnPropertyChanged(string propertyName)  
    {  
        var handler = PropertyChanged;  
        if (handler != null)  
            handler(this, new PropertyChangedEventArgs(propertyName));  
    }  
}  

Regards,
Kyle

---

If the response is helpful, please click "Accept Answer" and upvote it.

Note: Please follow the steps in our documentation to enable e-mail notifications if you want to receive the related email notification for this thread.